The present invention relates generally to a method of yarn piecing. More specifically, it relates to a method of yarn piecing in a spinning unit in which a so-called fasciated yarn is produced by the effect of fluid jets.
The process of spinning a yarn which includes core fibers having substantially no twist and peripheral fibers whose ends bind the core fibers is popularly referred to as the fluid jet process, and the resulting yarn as fasciated yarn. This spinning process has attained significant improvements in various respects recently and shown a remarkable increase in its spinning speed accounting for as high as 150 m/min.
In spinning such a fasciated yarn, fibers of sliver or roving are attenuated by a drafting mechanism including pairs of drafting rollers, and then transferred by fiber feeding rollers such as the front pair of the drafting rollers into an aspirator or a false-twisting nozzle, where the drafted fibers are subjected to rotating action by the flow of jetted fluid such as air. The fibers are twisted and then untwisted repeatedly in the false-twisting nozzle while they are advanced continuously through a yarn passage channel formed in the nozzle, thus being transformed into a strand of yarn which includes, as stated in the above, the core fibers having substantially no twist and the peripheral fibers binding said core fibers.
Such a double structure of fasciated yarn poses a problem in a yarn piecing operation performed for the purpose of repairing a break in the yarn. That is, due to the fact that the core fibers of the yarn have substantially no twist, it has been extremely difficult to connect either manually or mechanically the broken end of the yarn and the end of the fiber bundle by using a so-called splicing method in which the ends are joined by intermingling the fibers thereof and twisting them together securely. Accordingly, a knotter has usually been used instead for the purpose of yarn piecing in a fasciated yarn spinning unit. However, a joint formed in the yarn by knotting may cause a defect in the fabrics or knit goods produced in the subsequent weaving and knitting process. It has been a major concern, therefore, how to accomplish yarn piecing by splicing with ease and a high standard of reliability in a fasciated yarn spinning unit operated using a fluid jet process.
A method of yarn piecing by splicing in a fluid jet spinning unit has been disclosed by Japanese Unexamined Patent Publication No. 53-35033 (1978), said method of yarn piecing comprising the steps of introducing a broken end of yarn reversely through a false-twisting nozzle from its outlet, holding the end between a pair of front rollers of the drafting mechanism so as to allow the end to overlap the end of the fiber bundle, and then generating a rotary stream of air in the false-twisting nozzle, whereby the broken ends of the yarn and the fiber bundle are pieced together while they are passed through the false-twisting nozzle.
In this prior art method, however, the end of the yarn unwound from the package and inserted reversely into a yarn passage channel formed through the false-twisting nozzle may be caught by air jetting holes which are formed in the nozzle in a convergent arrangement toward the outlet of the nozzle along the yarn passage channel. Consequently, smooth passing of the yarn end through the channel is not only hampered, but also there is a fear of fiber pieces or impurities contained in the yarn blocking the delicately-drilled air jetting holes thereby to prevent the development of the normal rotary stream of air which is necessary for false-twisting the fibers in the bundle.
Furthermore, in accordance with this prior art method, the end of the yarn brought from its package is grasped at the outlet of the channel, whereupon it is released to be passed reversely through the channel and grasped again at the opposite inlet of the channel. In this way, yarn end grasping which is one of the most risky steps in yarn piecing must be performed twice, which will naturally decrease the rate at which the yarn piecing is accomplished successfully.